This invention relates generally to the assembly of coil springs of the type used in bedding and upholstery and, more particularly, to an improved apparatus for attaching end turns of a coil spring to a border wire.
In known assemblies of coil springs that are used in bedding and upholstery, adjacent rows of coil springs are connected by a helical lacing wire that is laced around adjacent portions of top and bottom turns of the coil springs. The lacing wire often extends from one side edge of the coil spring assembly to an opposite side edge to form a matrix of interconnected coil springs. In some applications, only the top turns or only the bottom turns are laced together. Thereafter, the coil spring matrix is converted into a completed coil spring assembly by attaching the coil springs to a border wire in either or both of the top and bottom planes of the spring unit. The border wire is generally a single heavy gauge wire preformed into a rectangular configuration and disposed in border fashion about the periphery of the coil spring matrix. The border wire is attached to the peripheral portion of the end turns of the spring coils by helical lacing wires, preformed metal clips, staples or separate lengths of straight wire. The attachment of the border wire to the matrix of coil springs is performed either manually or automatically.
At the present time, nearly all commercial fasteners used for attaching the border wire to the coil springs are sheet metal clips that are preformed and assembled into a string of clips. The string of clips is fed into a machine that applies the clips to a border wire and inner spring assembly being conveyed past the machine. The sheet metal clips have sharp edges and corners that often cause problems during the manufacturing process. For example, the corners of the clips can catch on fabric that is subsequently applied to the coil spring assembly. Any time fabric catches on a clip, some sort of special handling is required that adds cost to the manufacturing process. Further, any time the coil spring assembly is manually handled, care must be taken to avoid contact with the sharp edges and corners of the sheet metal clips.
Therefore, there is a need for an apparatus that connects coils springs to a border wire with fasteners that do not have sharp or pointed edges, corners or ends.
The present invention provides a wire cutting and wrapping apparatus that provides cut wire tips that are blunt. The wire cutting and wrapping apparatus of the present invention is especially useful for attaching coil springs to border wires in the manufacture of coil spring assemblies to be used for bedding and upholstery. By providing cut wire fasteners with blunt ends, a resulting coil spring assembly can be readily covered with a fabric without the fabric being unnecessarily caught or torn by the ends of the wire fasteners. In addition, the blunt tips of the wire fasteners provided by the wire cutting and wrapping apparatus of the present invention make the finished coil spring assembly much easier to manually handle.
According to the principles of the present invention and in accordance with the described embodiments, the invention provides an apparatus for attaching end turns of coil springs to a border wire. The apparatus has an indexable carriage adapted to move the coil springs and the border wire along a path. A wire cutter located adjacent the path has an inner member with an axial hole adapted to receive the wire and a tubular outer member receiving the inner member and movable relative to the inner member. The outer member has a cutting edge. An actuator is operatively connected to one of the inner member and the outer member to provide a relative rotation between the inner member and the outer member. That relative rotation results in the wire being sheared by the cutting edge to provide a length of wire. A wire wrapping mechanism located adjacent the wire cutter and the path receives the length of wire and wraps the length of wire around an end turn of a coil spring and a border wire.
In one aspect of the invention, the wire wrapping mechanism has a pair of gears rotatable with respect to a common axis of rotation. Each of the gears has a radial slot that receives an end turn of a coil spring and a border wire and a hole that receives the length of wire. A drive shaft is mechanically coupled to the pair of gears, and the drive shaft is operable to rotate each of the gears in a different direction to wrap the length of wire around the end turn of the coil and the border wire. In another aspect of the invention, the hole has a centerline nonparallel with respect to the common axis of rotation.
In another embodiment of the invention, a method is provided for attaching an end turn of a coil to a border wire. First, the end turn of a coil spring and a border wire are located in radial slots of respective gears, wherein the respective gears having a common axis of rotation. Next, a wire is fed through an axial hole of an inner member of a wire cutter. The wire cutter has a tubular outer member that receives the inner member, and the outer member has a cutting edge adjacent an end surface of the inner member. Next, the wire is fed through holes in the respective gears, and an actuator of the wire cutter is operated to provide a relative rotation between the inner member and the outer member. That relative rotation causes the cutting edge to pass over the axial hole of the inner member and shear the wire to a length. A drive shaft mechanically coupled to the two gears is then rotated to simultaneously rotate each of the two gears in a different direction and the length of the wire is wrapped around the end turn of the coil spring and the border wire located in the radial slots of the respective gears.
These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein.